hard · Order Flow Analysis market-mechanics-execution

Under the exchange's FIFO (price-time priority) matching, and given the trader's order is for 100 contracts, how many of the trader's contracts are filled after both market orders, and what does this imply about reading queue position from the footprint's bid-traded volume?

1. The trader gets 100 filled: the first 150-lot consumes the 200 ahead only partially (50 remain), the 300-lot then clears those 50 and fills the trader's 100 (200 still left to deeper queue), so the 450 bid-traded contracts printed at that level understate true resting depth and queue position cannot be inferred from traded volume alone.
2. The trader gets 0 filled, because under FIFO the 200 contracts ahead must be fully cleared by a single order and neither the 150 nor the 300 alone exceeds 200.
3. The trader gets 50 filled, because price-time priority allocates fills pro-rata across the queue and the trader's share of 300 lots after the 200 ahead is 50.
4. The trader gets 100 filled, but this proves bid-traded volume on the footprint exactly equals resting depth, so queue position is directly readable from the printed bid volume.

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